Diversification in Functions and Expressions of Soybean Genes Fine-Tunes Seasonal Flowering.

The proper timing of flowering in response to environmental changes is critical for ensuring crop yields. () homologs of the phosphatidylethanolamine-binding protein family play important roles as floral integrators in many crops. In soybean, we identified 17 genes of this family, and characterized biological functions in flowering for ten homologs. Overexpression of homologs in revealed that a set of homologs, including , , and , promoted flowering similar to ; in contrast, , , and delayed flowering. Consistently, expressions of , , and were induced in soybean leaves in response to floral inductive short days, whereas expressions of and were induced in response to long days. Exon swapping analysis between floral activator and floral repressor revealed that the segment B region in the fourth exon is critical for their antagonistic functions. Finally, expression analysis of , , and in soybean accessions exhibiting various flowering times indicated that the mRNA levels of and were higher in early flowering accessions than in late-flowering accessions, while showed the opposite pattern. Moreover, the relative mRNA levels between / and was important in determining day length-dependent flowering in soybean accessions. Taken together, our results suggest that the functions of homologs have diversified into floral activators and floral repressors during soybean evolution, and the timing of flowering in response to changing day length is determined by modulating the activities of antagonistic homologs.